1. Field of the Invention
This invention relates to semiconductor electronic devices and circuits such as integral electronic circuitry and more particularly to an improved apparatus and method for creating wide-bandgap semiconductor electronic devices and circuits with laser radiation.
2. Background of the Invention
Certain ceramics, such as silicon carbide (SiC) and aluminum nitride (AlN), are known to exhibit electrical properties ranging from insulating to semiconducting to conducting, as discussed in U.S. Pat. No. 5,145,741 issued Sep. 8, 1992, entitled xe2x80x9cConverting Ceramic Materials to Electrical Conductors and Semiconductorsxe2x80x9d issued to Nathaniel R. Quick, and U.S. Pat. No. 5,391,841 issued Feb. 21, 1995, entitled xe2x80x9cLaser Processed Coatings on Electronic Circuit Substratesxe2x80x9d issued to Nathaniel R. Quick. The wide-bandgap semiconductor phases of these ceramics and other wide-bandgap semiconductors including diamond, are used to create devices such as conductive tabs, interconnects, vias, wiring patterns, resistors, capacitors, semiconductor devices and the like electronic components by laser synthesis on the surfaces and within the body of such wide-bandgap semiconductor to thereby eliminate photolithography processes which require numerous steps and generate undesirable chemical pollutants when processing such traditional electronic devices, components and circuitry.
As is well known alumina (Al2O3) dominates the dielectric market as an integrating substrate or device carrier in electronics packaging. BN, AlN, SiC and diamond are also of interest, due to their Thermal Coefficient of Expansion (TCE) and for their dielectric constant and higher thermal conductivity than that of Al2O3. SiC, AlN, BN, GaN and diamond also exhibit a wide-band gap and chemical resistance; they exhibit semiconducting to insulating properties. These properties are of substantial interest for new high temperature, approaching 1000xc2x0 C. and aggressive environment applications, particularly where high integrated circuit packing densities are required. In the prior art, metallization methods, including dry-film imaging and screen printing have been used for the production of conductive patterns on alumina, however, metal compatibility with the newer high thermal conductivity ceramic materials such as AlN and SiC, have not completely solved. Copper and silver paste exhibits a TCE mismatch aggravated by high temperatures as well as being subject to oxidation that increases their resistivity. In particular, bonding of copper to AlN has proved to be nontrivial alumina or stoichiometric aluminum oxynitride it (AlON) coatings must be developed on the AlN surface through passivation processes. These passivation processes have poor reproducibility. Thus, the direct laser synthesis of conductors in AlN, SiC and diamond substrates appears to provide solutions to this long standing prior art problem with regard to metallization and for more simple processing techniques for creating devices and circuitry that are compatible with selected ceramic substrates, while satisfying the need for higher temperature, aggressive environment, and higher density integrated circuit packaging applications.
The present invention is defined by the appended claims with specific embodiments being shown in the attached drawings. For the purpose of summarizing the invention, the invention relates to the use of selected wide-bandgap semiconductors including the doping of the wide-bandgap semiconductor. The invention includes the use of laser synthesis processing techniques applied to selected areas of the wide-bandgap body for creating electronic component devices. The electronic component devices may be individual component or an interconnected circuit arrangement on the surface of or within a substrate body of wide-bandgap material.
In a more specific example of the invention, the present invention includes the use of laser synthesis processing techniques applied to selected areas of the wide-bandgap semiconductor materials, chemical doping of the wide-bandgap semiconductor materials, and use of laser synthesis processing techniques applied to selected areas of the wide-bandgap semiconductor body for creating electronic component devices individually and in an interconnected circuit arrangement on the surface of and/or within a substrate body of the wide-bandgap semiconductor material, such as for examples AlN, BN, GaN, SiC and diamond, whether the wide-bandgap semiconductor is thin film or bulk material. The invention uniquely utilizes the properties of the doped wide-bandgap semiconductor in combination with selected laser synthesis techniques to create a variety of electronic devices and components, such as capacitors; resistors; diodes; transistors; logic and digital devices; electrical conductors, connection tabs, conductive holes or vias through substrates; and various types of sensors. More specifically, by selectively chemical doping designated surface areas and layers of the wide-bandgap semiconductor substrate body or film with chemical elements, a wide-bandgap semiconductor is produced that may be readily converted in designated areas thereof by laser synthesis, using one of several laser devices, to create discrete electronic devices and electronic circuit arrangements. The creation of these various electronic devices and circuits takes place incrementally, such as making a (p-n)-type carrier semiconducting device by laser synthesizing two adjacent areas, one for the (p) and the other for the (n) portion. The required electrical conductive tab connections are laser synthesized on either side of the p-n junction, to thereby form a p-n junction diode. The formation of a simple (p-n-p) or (n-p-n) arrangement is accomplished by an added step in the above diode process by adding an additional (p) or (n) laser synthesized component, with the appropriate electrical conductor connections as noted above with respect to the diode example. Such elemental electronic devices are readily produced by simple laser synthesis without the traditional multiple step processing and attendant pollution and environmental contamination problems of the prior art processes.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifing or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.